The structures of (Sr,Ba)[(Al,Ga)2(Si,Ge)2O8]. III. The crystal structures of the paracelsian-like modifications of synthetic SrGa2Ge2O8 and BaGa2Ge2O8

Calleri, M.; Gazzoni, G.

doi:10.1107/s0567740876004937

Cited by 19 publications

(17 citation statements)

References 14 publications

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“…The individual T-O bonds also show significant scatterings from the mean values, both for BaGa2Ge2Os (Table 3a) (Table 4a; Calleri & Gazzoni, 1976).…”

Section: The Same Trend Of T-o(a2)-t Angles Is Shown To Varying Extementioning

confidence: 99%

“…It is interesting to note ( Table 5) that for BaGa2Ge2Os they are both significantly narrower than 131 ° which seems to be the value preferred by the natural feldspars (Megaw, 1974b). From the results obtained for the stability conditions of the fe]dspar and paracelsian forms (Gazzoni, 1973;Calleri & Gazzoni, 1975b), we may infer that a narrower (T-O-T) corresponds to a smaller stability field of the feldspar form.The individual T-O bonds also show significant scatterings from the mean values, both for BaGa2Ge2Os (Table 3a) (Table 4a; Calleri & Gazzoni, 1976). …”

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confidence: 99%

“…The thermal mo- tion is not very marked, but the anisotropy is appreciable and greater than for the gallosilicates of Sr and Ba. The ellipsoids of the cations have their longest axis parallel to one of the cell axes as in the paracelsian modification of BaGa2Ge2Os (Calleri & Gazzoni, 1976).R after the full anisotropic refinement is higher than that based on the 810 strongest reflexions; the standard (0000) 2755 (1) 3 (1) 670 (1) 19 (1) 37 (1) 13 (0) 1 (1) -1 (1) -1 (0) Ge(1) (0000) 32 (2) 1799 (2) 1083 (1) 20 (3) 27 (1) 6 (1) -3 (1) 4 (1) -1 (1) Ga(1) (0z00)13 (2) 1821 (2) 6155 (1) 20 (2) 29 (1) (0000) 6989 (2) 1222 (2) 1739 (1) 16 (3) 24 (1) 4 (1)6911 (2) 1152 (2) 6732 (1) 11 (2) 26 (1) 6 (1) 0 0 1 (1) O(A1) (0000) 19 (24) 1268 (11 (0000) 8282 (21) 1242 (14) 1056 (13) 85 (25) 46 (11) 29 ( (0z00) 8040 (21) 1306 (14) 6033 (11) 82 (24) 45 (10) 22 (8) -13 (12) 23 (12) 8 (7) O(C) (0O00)86 (21) 3066 (12) 1195 …”

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The structures of (Sr,Ba)[(Al,Ga)2(Si,Ge)2O8]. IV. The crystal structure of the synthetic feldspar BaGa2Ge2O8

Calleri¹,

Gazzoni²

1976

Acta Crystallogr Sect B

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The structure of the feldspar modification of BaGa2Ge2Oa has been found from diffractometer intensities and refined by Fourier and least-squares methods. The structure is similar to that of celsian:space group I2/c, Z = 8. The mean values for the four independent tetrahedra of the asymmetric unit are:(Ge(1) (0)-O)= 1.74, (Ge(2) (z)-O)= 1.74, (Ga(1) (z)-O)= 1"81, (Ga(2) (0)-O)= 1.82 A. These figures are compatible with the postulate of nearly complete Ga/Ge order. The strains in the tetrahedral bond angles are very marked, the angles varying between 96 and 118 °. The Ba ion can be considered sevencoordinated. The influence of different T and M cations on the framework of the 14 A monoclinic feldspars is examined. IntroductionThe structural investigation of the feldspar form of BaGa2Ge2Os has been performed as part of a programme of research on the phases of compounds with the general formula (Sr, Ba)[(A1, Ga)2(Si, Ge)208]. The present modification is metastable and was obtained only by cooling of the melt (Gazzoni, 1973); the structure of the stable, paracelsian-like, modification was described in part III of this series (Calleri & Gazzoni, 1976).The structures of a few 14 A monoclinic feldspars are known: synthetic SrA12Si208 (Chiari, Calleri, Bruno & Ribbe, 1975); synthetic SrGa2Si208 and BaGa2Si208 (Calleri & Gazzoni, 1975a); synthetic BaGa2Ge208 (present work); natural celsian, BaA12Si208 (Newnham & Megaw, 1960). We intend therefore to compare some dimensional features of these compounds, as has been done for three paracelsian modifications (Calleri & Gazzoni, 1976), looking for a correlation with the dimensions of the cations. Structure determination Experimental resultsWeissenberg and precession photographs showed only 'a-type' (h + k even, l even) and 'b-type' (h + k odd, l odd) reflexions and permitted the assignment of space group I2/e, assuming the presence of a centre of inversion at (000) by analogy with other 14 A feldspars (for example see Newnham & Megaw, 1960). The cell parameters were refined by least squares from 0 values measured on powder spectra taken with a focusing camera (Cu Kc~ radiation).The results are: BaGazGezOs, M=549.98, monoclinic, a=8.896 (6), b=13.528 (6), e=14.906 (6) A, fl= 114.87 (6)°; U= 1627.5 Aa; De =4"49 g cm-3; Z=8; space group I2/c; F(O00) --1968. Crystal dimensions: 0.160 mm across the opposite faces of {100}, 0-055 mm across the opposite faces of {010}, 0.115 mm between (001) and (104); p(Mo K~)= 195.5 cm -1.The intensities accessible to Mo Kc~ radiation, within 20=60 °, were collected at room temperature with a Philips four-circle diffractometer, equipped with a graphite monochromator, by the 0-20 step-scanning technique. The integration speed was 0.025 ° s -1 and the integration interval 1.5°; 1405 reflexions, out of 2164 explored, had I>_2a(1) and were included in the analysis; there were 420 b-type reflexions. The weaker reflexions were scanned four times and the measurements were averaged. The reflexions with I>_4a (1) were measured also with the 09 step-scann...

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“…The individual T-O bonds also show significant scatterings from the mean values, both for BaGa2Ge2Os (Table 3a) (Table 4a; Calleri & Gazzoni, 1976).…”

Section: The Same Trend Of T-o(a2)-t Angles Is Shown To Varying Extementioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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The structures of (Sr,Ba)[(Al,Ga)2(Si,Ge)2O8]. IV. The crystal structure of the synthetic feldspar BaGa2Ge2O8

Calleri¹,

Gazzoni²

1976

Acta Crystallogr Sect B

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“…On the other hand, given the M-cation type, an increase in the average T-cation size corresponds to an increase of the distortion: the aluminosilicates show the smallest and the gallogermanates the largest distortions both among the feldspars and the paracelsians. Experimentally, we * In previous papers (Calleri & Gazzoni, 1974, 1976a we used, for the T sites in the paracelsian framework, a notation different from that of Phillips, Kroll, Pentinghaus & Ribbe (1975). We labelled T(I)(m) and T(2)(0) the paracelsian sites allocating the trivalent T cations as for the feldspars.…”

Section: [T(2)]/~[t(1)]mentioning

confidence: 99%

“…SrA12G%Os ( Calleri & Gazzoni (1976b); (g) Kroll & Phillips (1976); (h) Calleri & Gazzoni (1974); Gazzoni (1976a), (j) Pentinghaus & Laves (1976). …”

Section: ((T-o)) (Mv~'-o) (T-o-t) (M-o)/((t-o))mentioning

confidence: 99%

The structures of (Sr,Ba)[(Al,Ga)₂(SiGe)₂O₈]. V. The crystal structure of the synthetic feldspar BaAl₂Ge₂O₈

Calleri¹,

Gazzoni²

1977

Acta Crystallogr Sect B

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Germanate Zeolites: Contrasting the Behavior of Germanate and Silicate Structures Built from Cubic T8O20 Units (T=Ge or Si)

1999

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A brief review of germanate-based zeolitelike structures is given. The frameworks of new germanates containing cubic Ge 8 O 20 clusters are analyzed in detail and compared with those of related silicates. It is shown that some topologies are suitable for silicates, but not for germanates; that others are suitable for germanates but not for silicates; and that a third class is suitable for both types of material.

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The structures of (Sr,Ba)[(Al,Ga)2(Si,Ge)2O8]. III. The crystal structures of the paracelsian-like modifications of synthetic SrGa2Ge2O8 and BaGa2Ge2O8

Cited by 19 publications

References 14 publications

The structures of (Sr,Ba)[(Al,Ga)2(Si,Ge)2O8]. IV. The crystal structure of the synthetic feldspar BaGa2Ge2O8

The structures of (Sr,Ba)[(Al,Ga)2(Si,Ge)2O8]. IV. The crystal structure of the synthetic feldspar BaGa2Ge2O8

The structures of (Sr,Ba)[(Al,Ga)₂(SiGe)₂O₈]. V. The crystal structure of the synthetic feldspar BaAl₂Ge₂O₈

Germanate Zeolites: Contrasting the Behavior of Germanate and Silicate Structures Built from Cubic T8O20 Units (T=Ge or Si)

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The structures of (Sr,Ba)[(Al,Ga)2(Si,Ge)2O8]. III. The crystal structures of the paracelsian-like modifications of synthetic SrGa2Ge2O8 and BaGa2Ge2O8

Cited by 19 publications

References 14 publications

The structures of (Sr,Ba)[(Al,Ga)2(Si,Ge)2O8]. IV. The crystal structure of the synthetic feldspar BaGa2Ge2O8

The structures of (Sr,Ba)[(Al,Ga)2(Si,Ge)2O8]. IV. The crystal structure of the synthetic feldspar BaGa2Ge2O8

The structures of (Sr,Ba)[(Al,Ga)2(SiGe)2O8]. V. The crystal structure of the synthetic feldspar BaAl2Ge2O8

Germanate Zeolites: Contrasting the Behavior of Germanate and Silicate Structures Built from Cubic T8O20 Units (T=Ge or Si)

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The structures of (Sr,Ba)[(Al,Ga)₂(SiGe)₂O₈]. V. The crystal structure of the synthetic feldspar BaAl₂Ge₂O₈